Alternating-current induction motor



Nov. 6, 1928. r 1,690,953

L. SCHON ALTERNATING CURRENT INDUCTION MOTOR O Filed Oct. 2. 1926 2 Sheets-Sheet 1' Nov. 6,1928. v 1,690,953

L. SCHON ,wrannmue cummur 'mnucnou uowon Filed Oct. 2. 1926 2 Sheets-Sheet 2 Patented Nov. s, 1928.

; UNITED STATES PATENT OFFICE.

LUDWIG solicit, or ESSEN, GERMANY, ASSIGNOR T FRIED. KRUPP AKTIENGESELL contain, or ESSEN-ON-THE-RUHR, GERMANY. a

ALTERNATING-GURBENT' INDUCTION MOTOR.

Application filed October 2, 1926, Serial No. 139,164, and in Germany March 13,

The invention relates to the alternating current induction motor described in our former application for Letters Patent Senal Number 13,827) filed March 7th, 1925, atent No. 1,675,960, July 3, 1928, and has for its object to so improve this motor that its manufacture is considerably simplified and its costs are lowered accordingly. This is obtained bthe fact that the auxiliary rotor carrying 10 tile exciting winding is arranged between the stator and the rotor and constitutes an iron body closed in circumferential directionand is provided on its outer and inner side with slots designed to receive the exciting windl5 m in the accompanying drawings is illustrated an embodiment of the improved motor by way of example. In these drawings:

Fig. 1 is a diagrammatic front view of the stator, auxiliary rotor and rotor,

Fig. 2 shows a wiring diagram of the motor.

A denotes the stator, B the rotor, and C the auxiliary rotor arranged between them. The stator A is provided on its inner side with 5 slots a lodging a winding (1 which is connected to a source I), Fig. 2, of single-phase alternating current. Part of the slots a which are left empty in Fig. 1, serve to receive an auxiliary winding a (auxiliary phase) which is operative only in the starting and is adapted to be switched oil by special means, Fig. 2. The rotor 13 carries a three phase winding 5 the ends of which are, on the one hand, in star connection with one another and, on the by which rings said ends are in connection with astarting resistance E, Fig. 2.

4 The auxiliary rotor C consists of a drum the iron shell of which has milled into it on the outer and inner side slots 0 arranged in pairs opposite each other and designed to receive the exciting winding 0 This winding 0 is connected to a source F of continuous have the same magnetic potential. Besides other hand, connected with three collector. rings 5 Fig. 2, mounted on the rotor shaft,

current, Fig. 2, and so arranged that the this, the auxiliary rotor carries in its slot 0 .a polyphase short-circuit shown'in Fig. 1 but in Fig.

In order to start the described motor, either without load or under load, the stator windmg 3 together with the said auxiliary phase a Fig. 2, is switched in first while the rotor winding 6 is open and the winding 0 of the auxiliary rotor unexcited. Under the action of the two-phase rotating field produced by the stator by means of the auxiliary phase and of the short-circuit currents in the winding 0 of the auxiliary rotor C, the latter starts in a' definite sense of rotation, viz, in the sense of the rotation of the rotating field produced by the auxiliary phase, and will soon reach a number different from synchronism. auxiliary phase is switched off, auxiliary motor G acts on the two oppositely revolving rotating fields, into which the single-phase alternating stator field may be thought resolved according to a common view, in such a manner that the rotating field revolving in the sense of rotation of the auxiliary rotor C is considerably boosted, while the oppositely revolving rotating field is caused to practically disappear. By the cooperation of the rotating field revolving in the same sense as the auxiliary rotor, with the shortcircuit current induced in the auxiliary rotor a turning moment is generated by which the rotation of the auxiliary rotor and thus the rotating field itself, revolving in the same sense, are maintained. It, now, the exciting winding 0 arranged on the auxiliary rotor C is connected with the source F of continuous current, the auxiliary rotor C becomes in a manner the rotor of a. synchronous motor by rotating synchronously, with the operative rotating field of the stator and taking in this rotating field such a position that opposite poles follow each other on the magnetic path of the lines of force, which means that e. g. a north pole of the stator is opposite to a south pole of the auxiliary rotor and that the north pole, allotted to said south pole, of the auxiliary rotor, is opposite to a south pole of the rotor. The maintenance of the rotating field revolving in the same sense as the auxiliary rotor is thus secured even when the motor is considerably oyerloaded. This fact renders it possible to start the rotor B by means of starting resistances exactly in the manner as the rotor of a multiphase motor. For, as the exciting winding c is so chosen, as described winding 0 not It, now, the

the revolving of revolutions not very above, that no difference of potential exists motor, or the of the current with ard to in the direction of the circumference of the the tension may converted intoal of the auxiliary rotor, the magnetic flux in the latcurrent.

.ter in the direction of the circumference is I claim:

subdued. Hence, the rotating field revolv- An alternating current induction motor ing in the stator is forced to traverse the auxcomprising a stator, a rotor and an auxiliary iliary rotor in radial direction and to close itrotor arranged between the stator and rotor self through the rotor B, so that the rotor and consisting of a drumhavinganiron shell winding is linked with said rotating field provided on its inner and outer side with exactly as in a multiphase motor. In order slots, a stator winding and a rotor winding to obtain the turning moment required for one of said windings being connected to a starting the motor, it is, therefore, only necessource of alternating current, a short circuit sary to close the rotor winding 6 by switch armature winding carried by the auxiliary ing in the starting resistances E, Flg. 2, a rotor,'and an exciting winding arranged in comparatively high mechanical load of the the inner and outer slots of said iron shell in motor being admissible, as a starting turning such a manner that in the central portion of moment constituting a multiple of the norsaid shell corresponding points which are dismal turning moment may be easily obtained. tant from each other by the distance of adja- According to the strength chosen for the excent poles have the same magnetic potential,

citing current in the winding 0 the phase the magnetic flux generated by said exciting displacement between the strength and the winding passing through the stator, the auxtension of the single-phase current supplied iliary rotor and the rotor in a path traversing to the stator winding of may be influenced the auxiliary rotor in radial direction.

as desired the same as m an ordinary syn- The foregoing specification signed at chronous motor. Therefore this phase-dis- Cologne, Germany, this 9th day of Septemplacement may, for instance, be reduced or her, 1926.

entirely removed, which means that a power factor of cos p=1 may be imparted to the LUDWIG SCHON. 

